JP4186781B2 - Assembled battery - Google Patents

Description

  The present invention relates to an assembled battery that is optimal as a power source that supplies large energy with high energy density, small size, and light weight.

  In recent years, in response to growing environmental awareness, there is a movement to shift the power source of automobiles from an engine using fossil fuel to a motor using electric energy. For this reason, the technology of the battery that serves as a power source for the motor is also rapidly developing.

  An automobile is desired to be mounted with a battery that is small and light and can be charged and discharged with a large amount of electric power and has excellent vibration resistance and heat dissipation. As an assembled battery excellent in heat dissipation capable of supplying large electric power, there is a battery as shown in Patent Document 1 below.

  The assembled battery disclosed in Patent Document 1 includes a plurality of unit cells that are electrically connected in series, parallel, or series-parallel at predetermined intervals in the thickness direction of the unit cell, and both sides between the unit cells. A pressing member that presses the single cell is disposed, and a plurality of single cells are fixed by an exterior member. By adopting such a structure, the heat dissipation characteristics of the single battery are improved, and the cycle characteristics and rate characteristics of the assembled battery are improved.

In such an assembled battery, after fixing a cell to an exterior member and laminating | stacking up and down, the electrode tabs protruded from each cell are connected by the connection member (refer the following patent document 2).
Japanese Unexamined Patent Publication No. 2000-195480 (see paragraph number “0014” to paragraph number “0029”, paragraph number “0040”, paragraph number “0041” and the descriptions in FIGS. 1, 2, and 4) Japanese Patent Laid-Open No. 7-183022 (see paragraph number “0008”, paragraph number “0019” and the description of FIGS. 1, 2, 4, and 5)

  Since the assembled battery of Patent Document 1 uses a flat battery as a single battery, the battery has the same energy capacity and higher energy density than a conventional assembled battery configured using a battery other than the flat battery. If so, downsizing is possible. For this reason, the assembled battery comprised by the flat type battery is suitable as a battery for vehicle mounting in terms of small size and high energy density.

  However, since this assembled battery is an assembled battery developed for a power storage system, it is necessary to greatly improve its structure to be used as an assembled battery for a vehicle that requires production efficiency and reduction in size and weight. .

  In order to solve this problem, for example, as described in Patent Document 2, a plurality of flat unit cells are placed on one plane, and the unit cells are connected to each other by connecting the plurality of unit cells to each other. Then, it is conceivable to form a small, light, and highly efficient assembled battery by stacking a plurality of unit assembled batteries and connecting them to each other. The connection between the plurality of single cells in such an assembled battery is performed by welding the conductive member to the electrode tab (electrode terminal) of each single cell.

  However, when connecting each cell by welding the electrode tab and the conductive member as described above, after welding the electrode tab of one unit cell and one end of the conductive member, the electrode tab of another unit cell When the electrode tab of another unit cell and the other end of the conductive member are welded, if vibration is applied to the other end, the applied vibration is applied. May be transmitted to one end of the conductive member, and the welding of the one end of the conductive member already welded to the electrode tab may be peeled off or a connection failure may occur at the welded part. In addition, when welding the other end of the conductive member, it may be possible to prevent vibration by fixing the one end of the conductive member and the electrode tab together with a jig or the like. Each time the other end is welded, it is necessary to fix it with a jig or the like between the one end of the conductive member and the electrode tab, and there is a problem that welding workability is poor.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an assembled battery that can be used as an assembled battery for a vehicle and is advantageous in terms of welding workability.

In order to achieve such an object, the assembled battery of the present invention includes at least a pair of flat unit cells, an electrode tab as an electrode terminal of the unit cell protruding in a direction perpendicular to the thickness direction of each unit cell, An electrode tab of one unit cell of each unit cell and a connection member that electrically connects the electrode tabs of the other unit cells to each other, and the connection member includes at least the one unit cell. Resonance prevention means for preventing resonance between a junction with the electrode tab of the battery and a junction with the electrode tab of another unit cell is provided.

In the assembled battery of the present invention, one end of the connection member is welded to the electrode tab of one unit cell, and the other end of the connection member is joined to the electrode tab of another unit cell by ultrasonic welding. In this case, the resonance point between the one end and the other end of the connecting member is shifted, thereby preventing a large vibration.

  Hereinafter, embodiments of an assembled battery according to the present invention will be described with reference to the drawings. First, a single cell used in the assembled battery will be described, and the structure of the assembled battery and an electrode tab for constructing the assembled battery will be described. The welding of the connecting member will be described.

<Single cell>
FIG. 1 is a perspective view showing a unit cell. As shown in FIG. 1, the unit cell B used in the present embodiment is a rectangular flat secondary battery, and includes a power generation element (not shown) in which a positive electrode plate, a negative electrode plate, and a separator are sequentially stacked. 1 has a plurality. This power generation element is, for example, a lithium ion secondary battery.

  The exterior material 1 used here is, for example, a laminated film having a three-layer structure in which an aluminum foil is sandwiched between resin films such as polyamide resin. In forming the flat unit cell B, Two laminate films are prepared, one is formed into a flat bowl shape by pressing, the other is used in the form of a sheet, the power generating element is installed between the laminate films, and the periphery is heat-sealed. And sealed. Hereinafter, such a flat cell B is simply referred to as a cell B.

  From the packaged unit cell B, for example, a positive electrode tab Ta made of a thin aluminum plate having a thickness of about 0.2 mm and a negative electrode made of a copper thin plate having a thickness of about 0.2 mm, for example. Although the electrode tab Tb is drawn out to the outside, in this embodiment, a single cell of a type in which electrode tabs T (electrode tabs Ta and Tb) having different polarities are drawn from two opposite sides is used. An assembled battery is configured.

<Structure of assembled battery>
FIG. 2 is a schematic perspective view of the assembled battery according to the present embodiment, and FIG. 3 is a schematic perspective view showing a state in which the unit cell is provided on the frame.

  Outlined about the assembled battery 10 according to the present embodiment, as shown in FIGS. 2 to 4, four unit cells B are arranged in a plane direction on a flat frame F, and these unit cells B are connected in series. A plurality of layers are stacked, and are pressed and held integrally from both sides in the stacking direction by holding means 11 (see FIG. 4).

  As shown in FIG. 3, the frame F is formed with a support frame f that supports the peripheral portion of the unit cell B, and the unit cell B is placed on the frame F. An opening O that is slightly smaller than the size of the unit cell B is provided inside so that the exterior surface is in direct contact.

  The four single cells B placed on the frame F are positioned by the support frame f, but the electrode tabs Ta and Tb are located on the support frame f and do not protrude from the periphery of the frame F to the outside.

  In the four unit cells B of each frame F, the electrode tab Ta of the + electrode and the electrode tab Tb of the − electrode of each unit cell B adjacent to each other are connected in series via the connection member 20 which is a conductive member. This connection is made by ultrasonic welding. The connection member 20 will be described in detail later.

  Since the assembled battery of this embodiment is obtained by stacking 24 layers of the frame F provided with the four unit cells B and connecting a total of 96 unit cells in series, each of the four unit cells B mounted thereon. The frames F are stacked in 24 layers, and the frames F are connected in series.

  There are various methods for connecting the frames F. In this embodiment, as shown in FIG. 4, a frame Fa in which a conductive washer Wa is embedded at an end and a frame Fb in which an insulating washer Wb is embedded are used. Do it. In this method, the frame Fa and the frame Fb are alternately stacked, and the electrode tabs Ta and Tb are in contact with the washers Wa or Wb of the respective layers to form an electrical series connection. In FIG. 4, only three layers are stacked, but actually six layers are stacked, the intermediate heat sink H3 is placed, and the same operation is repeated.

  FIG. 4 is a cross-sectional view taken along the line AA or A′-A ′ in FIG. 2, but the holding means 11 shown in FIG. 4 is not shown in FIG. 2 for convenience of explanation.

  As shown in FIG. 4, the holding means 11 includes a through bolt 15, a nut 16, and upper and lower heat sinks H1 and H2. The lower end of the through bolt 15 is fixed to the lower heat sink H2. Yes.

  The heat sinks H1 and H2 at the upper and lower ends are hard and are made of a porous material or a metal plate having a passage inside so as to exhibit heat dissipation, so that a predetermined surface pressure is applied to each unit cell. ing. A conducting member 17 is provided in the through hole of the upper end heat sink H1 through which the through bolt 15 is inserted.

<Assembly of assembled battery>
In order to assemble the assembled battery 10, first, as shown in FIG. 3, the four unit cells B are placed on the support frame f of the frame F in the surface direction and positioned. The electrode tabs Ta and Tb of each unit cell B are positioned on the frame F, and the connection member 20 made of a conductive member having a plate shape is placed on the electrode tab Ta and Tb. Ultrasonic welding with Tb. This ultrasonic welding will be described in detail later.

  As shown in FIG. 4, the battery unit composed of the frame F and the four unit cells B formed in this manner is stacked while passing the washers Wa and Wb of each frame F through the bolts 15. Since the through bolts 15 are erected on the heat sink H2 on the lower end side of the holding means 11, the battery units are placed on the upper surface of the heat sink H2 on the lower end side and stacked one after another.

  When six layers of battery units are stacked, the intermediate heat sink H3 is placed. This operation is repeated to stack 24 battery units.

After the completion of the stacking of the battery units, the upper end heat sink H1 is placed thereon, and the nut 16 is attached to the through bolt 15 and tightened. By this tightening, a predetermined surface pressure is applied to each unit cell B through the heat sinks H1 and H2 at the upper and lower ends. The tightening of the through bolt 15 is also performed at the unit cell B located at the end. Since the electrode tabs Ta and Tb protruding from the washers Wa and Wb are also electrically connected, the assembled battery 10 in which a predetermined number of all the cells B are connected in series is constructed. Become.
<Welding of electrode tab and connecting member>
In this assembled battery 10, the electrode tab T and the connection member 20 are welded and connected by ultrasonic welding. This is due to the following two reasons.

  The first reason is that ultrasonic welding performs mechanical joining by diffusing and recrystallizing metal atoms by applying high-frequency vibrations to the parts to be joined. Very effective against. In the unit cell of the present embodiment, the electrode tab Ta of the + electrode is an aluminum thin plate, the electrode tab Tb of the − electrode is a copper thin plate, and the connecting member 20 (commonly referred to as a bus bar) is made of copper. It becomes joining.

  The second reason is that ultrasonic welding does not reach a high temperature during joining, and the maximum temperature of the joining surface can be suppressed to about 35 to 50% of the melting point. No melting or brittle cast structure is formed. The unit cell used in the present embodiment is made of a very thin metal without exposing the unit cell B to a high temperature state because the exterior material is a laminate material and the electrode tab T cannot be raised to a very high temperature. It is most suitable for joining the electrode tabs T.

  When welding the electrode tab T and the connection member 20 by ultrasonic welding, first, one end of the connection member 20 and the electrode tab are welded, and then the other end of the connection member 20 and the electrode tab are welded. However, if the vibration generated during welding of the other end of the connection member 20 and the electrode tab is transmitted to the electrode tab T, various problems such as poor connection and weld peeling may occur. It is preferable to avoid transmission of vibration from one end of the connecting member 20 to the other end as much as possible.

  For this reason, in this embodiment, the form of the connection member 20 is improved and the vibration-proof property is high. Details will be described below.

  FIG. 5 is an explanatory view showing a state in which the connecting member is arranged in a polar coordinate system when determining the form of the connecting member, FIG. 6 is a front view showing the form on the YZ plane, and FIG. 7 is a front view showing the form on the XZ plane. FIG. 8 is a front view showing the form on the XY plane.

As shown in FIG. 5, the inventor tried to analyze vibration of a connection member 20 formed of a conductive member having a plate-like outer shape formed in a U shape so that the center portion is convex. In the connection member 20, the welding surfaces with the electrode tab T are A and B, the centers of A and B are the reference points a and b, and the center point of the line segment connecting the reference points a and b is c (m1). = M2). The center point c is the center of the convex portion of the connection member 20 and also the center of gravity of the connection member 20.

  As shown in the figure, when the connecting member 20 is arranged in a polar coordinate system and viewed from each plane (YZ, XZ, XY), how much the amount of deviation | λ | In other words, the resonance suppression effect due to the deviation amount | λ | was compared under various conditions.

  Here, the shift amount | λ | is an inclination angle or a protruding margin on each plane. The mating joint is, for example, the “b” point when the “a” point is first ultrasonically welded.

First, in the YZ plane shown in FIG. 6, the angle of each pieces of the connecting member 20 shall be the "α", "β", "γ", "δ". As shown in the figure, “β” and “γ” are internal angles of the first inclined portion 22a or the second inclined portion 22b with respect to the surface formed by the flat portion 21 of the convex portion, and “α” and “δ” are convex portions. It is an internal angle of the both ends in the top part 23. As initial conditions, β = π / 2 and γ = π / 2 are set, and after point a is ultrasonically welded, point b is ultrasonically welded. However, it is assumed that β + γ = π and the total volume of the connecting member 20 after the shape change does not change.

  Under this initial condition (β = π / 2, γ = π / 2), when point a is ultrasonically welded and then point b is ultrasonically welded, vibration generated during ultrasonic welding of point b is a. Since there is a possibility that welding peeling may occur, the angle β is gradually reduced (π / 2 → π / 6), and the angle γ is increased (π / 2 → 5π / 6). As shown in Table 1, the vibration suppressing effect is increased, but the manufacturability (including not only the workability but also the manufacturing cost) is lowered, and it is understood that an intermediate angle is preferable.

  On the other hand, when the connecting member 20 is formed by pressing, it is preferable that the angle γ is increased because it is substantially difficult to form, so that the angles α and δ are obtuse angles and the angles β and γ are acute angles. The connecting member 20 on the YZ plane preferably has a small angle β and the angles α and δ are obtuse.

  Therefore, from the manufacturing aspect, the shape of the connecting member 20 is two flat portions 21 having a planar shape to be a joint portion to be joined to each electrode tab T, and the first acute portion β from one flat portion 21. The inclined first inclined portion 22a, the second inclined portion 22b inclined from the other flat portion 21 by the second acute angle γ, and the inclined portions located between the first and second inclined portions 22a and 22b. The portions 22a and 22b are preferably formed to have a top portion 23 provided to have a predetermined obtuse angle.

  In the connection member 20 formed in this way, when one end is welded and the other end is joined by ultrasonic welding, the deformation of both the inclined portions 22a and 22b absorbs the generated vibration. Thus, the effect of preventing vibration transmission can be obtained, and the transmission of vibration to one end portion can be prevented to function as vibration transmission preventing means for preventing the vibration of the one end portion.

  Further, since the connection member 20 is asymmetric with respect to the plane Za-Za passing through the center point c, the resonance point between one end and the other end of the connection member 20 is also shifted, thereby preventing a large vibration. It also functions as a resonance prevention means.

Therefore, in this embodiment, when the shape of the connecting member 20 is deformed in the middle of the joints at both ends and the vibration isolator 30 is formed, the other end is ultrasonically welded while the one end is welded. The vibration transmission preventing means for preventing the vibration transmission when joining is performed, and the angles β and γ between the inclined portions 22a and 22b of the connecting member 20 and the flat portion 21 are not equalized, and each electrode tab. Assuming that the asymmetric structure is not symmetrical with respect to the plane Za-Za passing through the center between the joint portions of T, this serves as a resonance preventing means for preventing resonance between one end and the other end of the connecting member 20. The function can be added to the vibration isolator 30, and the vibration preventing means having both the vibration transmission preventing means and the resonance preventing means is provided.

  Next, on the XZ plane shown in FIG. 7, the vibration suppressing effect and manufacturability in the state where the convex portion of the connecting member 20 is inclined by the angle α (the state shown by the broken line in FIG. 7) were verified. In this case, since the center position c between the welding points a and b does not greatly deviate, as is apparent from Table 2, although the vibration suppressing effect is obtained, the effect is small. Further, in terms of manufacturability, it is necessary to bend one plate three-dimensionally, which is not preferable in terms of cost. In particular, the connecting member 20 may protrude from a battery area having a predetermined size, which may result in a volume loss when an assembled battery is used.

  Finally, on the XY plane shown in FIG. 8, assuming that the connecting member 20 does not have a convex portion, the shape is shifted from the center of gravity c by τ in the + Y direction and further shifted by τ in the −X direction. Table 3 shows the vibration suppressing effect and the like of this shape.

  The vibration suppression effect is good because it is deviated from the center c of the welding points a and b, but becomes a volume loss when an assembled battery is used. However, the processing is good because only one flat plate is punched out.

  As a result of such verification, the shape of the connecting member 20 is deformed as in the present embodiment in the middle of the connecting member 20 when one end is welded and the other end is joined by ultrasonic welding. Is applied, vibration generated at the other end is not transmitted to one end, and the resonance point is shifted between one end and the other end of the connection member 20 due to vibration applied to the other end. Thus, it is possible to prevent the occurrence of large vibrations at one end and to form the vibration isolator 30 that can prevent the occurrence of peeling of the weld at the electrode tab.

  For example, as shown in FIG. 9, the connecting member 20 has a small angle β between the flat portion 21 joined to each electrode tab T and the first inclined portion 22a, and the other flat portion 21 and the second inclined portion 22b. The angle γ may be modified so that it is not symmetrical with respect to a plane (corresponding to Za-Za) passing through the center between the joints in a relation of β <γ.

  In the embodiment, the straight connection member 20 itself is deformed in order to improve the vibration proof property. However, the width and thickness of the intermediate portion may be changed as appropriate. Furthermore, if the material of the connection member 20 is a softer material than the material of the electrode tab, the connection member 20 itself is deformed, and the same vibration suppressing effect as described above can be exhibited.

  The present invention is not limited to the above-described embodiments, and various modifications can be used within the scope of the claims. For example, although the said embodiment is related with the connection member which connects the electrode tab of an assembled battery, it is not limited only to this, It can be used also for the various thing to which ultrasonic welding is applied. .

  In the present invention, when the electrode tab of the unit cell is ultrasonically welded by the connecting member, the connecting member is provided with a vibration isolating portion to prevent the vibration of the welded portion from being transmitted to the battery body and the like. It is possible to prevent weld peeling due to this, and it is extremely advantageous in terms of workability to form an assembled battery having a plurality of welded portions.

It is a perspective view which shows a cell. It is a schematic perspective view of the assembled battery which concerns on this invention. It is a schematic perspective view which shows the state which provides a cell in a flame | frame. It is sectional drawing which follows the AA or A'-A 'line | wire in FIG. It is explanatory drawing which shows the state which has arrange | positioned the connection member in the polar coordinate system. It is a front view which shows the form of the connection member in the YZ surface of FIG. It is a front view which shows the form in the XZ surface of FIG. It is a front view which shows the form in the XY plane of FIG. It is a perspective view which shows the specific form of a connection member.

Explanation of symbols

10 ... assembled battery,
20: Connection member,
21 ... Flat part,
22a ... 1st inclination part,
22b ... 2nd inclination part,
23 ... the top,
30 ... Anti-vibration part,
α, δ… obtuse angle,
β ... the first acute angle,
γ ... second acute angle,
B ... Single cell,
c: Center point,
Ta, Tb ... electrode tab,
Za-Za: A plane passing through the center point between the joints.

Claims (9)

At least a pair of flat cells,
Projecting in a direction orthogonal to the thickness direction of each unit cell, an electrode tab as an electrode terminal of the unit cell,
A connection member for electrically connecting an electrode tab of one unit cell of each unit cell and an electrode tab of another unit cell;
Have
The connection member is provided with a resonance preventing means for preventing resonance between at least a junction between the electrode tab of one unit cell and an electrode tab of another unit cell. The assembled battery. At least a pair of flat cells,
Projecting in a direction orthogonal to the thickness direction of each unit cell, an electrode tab as an electrode terminal of the unit cell,
A connection member for electrically connecting an electrode tab of one unit cell of each unit cell and an electrode tab of another unit cell;
Have
The connection member includes vibration transmission preventing means for preventing transmission of vibration between a joint between the electrode tab of the one unit cell and a joint between the electrode tab of another unit cell, and between the joints. An assembled battery comprising vibration preventing means integrally formed with resonance preventing means for preventing resonance in the battery.   The assembled battery according to claim 1 or 2, wherein the resonance preventing means is formed asymmetrically with respect to a surface of the connecting member passing through a center point between the joints. The connection member is made of a conductive member having a plate-like outer shape,
The assembled battery according to claim 2 , wherein the vibration transmission preventing means includes a convex portion formed by bending the conductive member in a U shape between the joint portions. The connection member is made of a conductive member having a plate-like outer shape,
The vibration preventing means is characterized in that a convex portion formed by bending the conductive member into a U -shape is formed asymmetrically with respect to a plane passing through a center point between the joint portions. 2. The assembled battery according to 2 . The connection member includes two flat portions having a planar shape which is a joint portion with the electrode tab of the one unit cell and a joint portion with the electrode tab of another unit cell,
The convex portion has two inclined portions formed by bending so that an inner angle with respect to a surface formed by the flat portion is an acute angle, and an inner angle at an end portion of the two inclined portions is an obtuse angle. The assembled battery according to claim 4, wherein the battery pack comprises a bent top portion. The connection member includes two flat portions having a planar shape which is a joint portion with the electrode tab of the one unit cell and a joint portion with the electrode tab of another unit cell,
The convex portion includes a first inclined portion formed by bending an end portion of one flat portion of the two flat portions so that an internal angle with respect to a surface formed by the flat portion is an acute angle. The end portion of the other flat portion of the flat portion is formed by bending so that the inner angle with respect to the surface formed by the flat portion is a second acute angle different from the first acute angle. a second inclined portion, and consists of a top portion interior angles are formed by bending so that the obtuse angle at the end of the two inclined portions, the convex portions passing through the center point between the two junctions 6. The assembled battery according to claim 5 , wherein the battery pack is asymmetric with respect to the surface. The material of the connecting member is assembled battery according to any one of claims 1 to 7, characterized in that from the material of the electrode tabs is soft material. Wherein the bonding of the connecting member and the electrode tab, the assembled battery according to any one of claims 1 to 8, characterized in that by ultrasonic welding.

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